Conventionally, multirate digital multiplexing device and digital demultiplexing device can perform digital demultiplexing and digital multiplexing of signals with various bandwidths using combination of a subfilter and a Fourier transform (or fast Fourier transform: FFT) unit. Technologies related to the multirate digital multiplexing device and digital demultiplexing device are disclosed in Patent Literature 1 and Non Patent Literature 1 mentioned below.